What do people like, buy, and do? Companies and health organizations spend millions on surveys, polls, and focus groups in attempts to figure this out. Turns out those techniques aren’t that accurate.

But you know what is? Brain scans, suggests a new study showing how neural activity predicts people’s responses to public service ads about cigarette smoking. ScienceNOW reports.

The neurons in the medial prefrontal cortex (MPFC) at the front of your brain plays a role in self-reflection, thinking of what you value, and identity. This region’s activity increases when you see or try to determine the value of something, as it relates to you.